I was trying today some OCZ RAM (PC-8500 Dual Channel SLI Ready black heatspreaders) and I was able to run it with only 1.90V set in BIOS @DDR2-1066.

However I noticed some vdimm fluctuation. Everest is not the most accurate way to monitor this, but since neither BIOS or Easytune show current readings it's the only thing I have right now.

With 2.00V (+0.20V) I saw the readings stay at 2.06V, sometimes going down to 2.05V. Less changes...
With 1.95V (+0.15V) I saw it stay between 1.97~1.98V. More different readings.
With 1.90V (set in BIOS +0.10V) I saw vdimm stay at 1.92V, but fluctuate between 1.90~1.94V and different readings happened even more.

So, it seems the lower the vdimm, the more fluctuation.
Well, I don't think this fluctiation is good for RAM. If someone could test this...